NGC6760
 6 iterations.
Chebyshev coeffients a(0)T_0(u)+a(1)T_1(u)+..., where u is log (r/arcsec) mapped to [-1,1]
 a(0)=    20.551 +-  0.132
 a(1)=     2.159 +-  0.207
 a(2)=     0.266 +-  0.176
Power-of-x coeffients a(0)+a(1)x+a(2)x^2+..., where x=1+(r/r_c), r_c=1.35
 a(0)=     8.3822
 a(1)=     0.9993
 a(2)=     0.4431
log r(arcsec)   mu_V    mu_V(fitted)  residual   weight  data set